Process for drying hops



June 6, 1950 v. BLQXHAM 2,510,372

PROCESS FOR DRYING HOPS Filed March 29, 1948 IYIIIIIIII I III/III IIIIIIIIIIIII 1 gi Z INVENTOR.

Var/in A. B/OX/767/77 ATTORNE Patented June 6, 1950 PROCESS FOR DRYINGHOPS Verlin A. Bloxham, Berkeley, Calif.

Application March 29, 1948, Serial No. 17,655

6 Claims. (Cl. 3410) 1 This invention relates to a process for dryinghops.

The process commonly employed in drying hops involves the use ofapparatus including a houselike structure having a reticulated floorupon which the hops are loaded. This floor may be some 20 feet above theground. Beneath the floor is disposed a heater burning fuel of one sortor another. The products of combustion from the heater usually passthrough a zig-zag or similar arrangement of pipes, located perhaps 8feet beneath the floor on the way to the chimney. Forced draft of air isnot provided, but the house is built tall enough, compared to itssection, to provide a stack eflect. p

In order to dry a quantity of hops, the hops are first loaded on thefioor to a limit depth of about 24 inches. The heater is then fired upand maintained hot for a sufiicient period of time to allow the hops todry.

There are a great number of objections to this manner of drying, and tothe hop drier itself. One of the main objections is the variable qualityof the dried product. This variable quality is due to several factorsinherent in the process and apparatus. One of the main ones is thatdrying is more efilcient in the lower portion of the bed, due largely tothe slow passage of air through the bed. The result of this is that ifthe bed is not turned one or more times during the 2 tremely sensitiveto excessive temperature. Furthermore, this radiant heat raises thetemperature of portions of the enclosure which are seen by the pipes toexcessive levels. This results in the successive drying, charring andperhaps final combustion of the combustible material, generally wood,employed in construction of the drier. At least the loss of the driersby fire is a common drying process, the product will not be uniformly. a

dried.

The turning of the hops, in order to overcome lack of uniformity indrying, has its own drawbacks. Afer the hops dry, they become veryfragile and brittle and are easily broken, and when the bed is turned,in order to reverse positions of the upper and lower layers, many of thecones which have reached the brittle stage will be broken, and theproduct taken finally from the drier will have an excessively highproportion of fines. The labor involved in these extra operations isalso objectionable.

occurrence.

A further serious objection to the apparatus is encountered in the factthat fines fall from the hops through the fioor and onto the hot pipeswhere they become charred and give rise to vapors which in turn passthrough the hops and may be condensed on or absorbed by them.

Since the driers are so tall, the difiiculty, and labor involved inloading, turning, and unloading is considerable. Floor loading islimited to about 24 inches, since heavier loading unduly restricts flowof air. The heater is inemcient, as much as 50% of the heat going out ofthe stack. It is an object of my invention to provide a new and improvedprocess for drying hops, which process avoids the enumerateddisadvantages of the present process.

A further object of my invention is to provide a hop drying apparatusfor carrying out my new process, the apparatus being very eflicient andeffective in operation.

A further object of the invention is to provide a process resulting in agreatly superior product.

Other objects will become apparent in the following description.

The apparatus is shown in the drawing Figure 1 of which is a plan, theenclosure being sectioned below the hop floor.

Figure 2 is an elevation with parts in section.

In the drawing, the reference numeral I 0 refers generally to theenclosure or drying house. This house has four walls, as shown, a gableroof II, a reticulated drying floor l2, and in the apex of the roof anair outlet l3. An air inlet I l is provided above the level of the hops,for reasons which will be presently described.

The apparatus for applying drying gas to the house is indicatedgenerally by the numeral 20. This includes a burner 2|, in this instancea gas burner, and a blower 22 with its motor 23. Near the burner 2| isan air inlet 24 which admits air to support combustion of the gas, andalso additional air to be mixed with the products of combustion.

Between the blower 22 and house there is provided an outlet valve 25.Dampers 26 may be so operated as to close of! the conduit. Within theplenum under the drying floor I2 is a plurality of outlets 21 so locatedand arranged as to secure a maximum of uniformity of distribution of thedrying gas to the bottom of the floor l2.

A diffuser indicated at 28 is used between the burner and the plenum tosecure efiicient mixture of the incoming air with the products ofcombustion. Suflicient air is taken in through the inlet 24 to mix withthe products of combustion and the hot gases so that the temperature ofthe mixture is within a suitable range.

The dampers 26 are used mainly to cut off the flow into the drierwhenever this is desirable, as for example, when the apparatus is justbeing started up and the products of combustion may include smoke or thelike which should not be sent through the hops. With the dampers 26closed and the valve 25 open, the gases may be by-passed to atmosphere.

The opening l4 may be provided at any point under the roof and over thelevel of the hop bed, but ordinarily on the side of the house from whichcome the prevailing winds. The purpose of this opening I4 is to allowingress of atmospheric air to the space above the hops. The air passingthrough the hop bed evaporates and thus contains a considerable amountof moisture, and in certain stages of the drying, the relative humidityof the air passing from the bed and out the opening 13 may be well uptoward 100%. If such conditions obtain for any length of time, moisturemay condense on the roof and other exposed and perhaps cool portions ofthe enclosure. To prevent this, the outside air dilutes the humid air.To this end, the openings l3 are of sufficient size relative to thequantity of air passing therethrough that additional air may be easilyforced in by even a slight breeze from the direction which appliespressure to the opening I4.

I have contemplated that a slight aspirating effect may be obtained bythe air passing through the bed and through the openings l3 so thatopenings or louvers l4 need not be in any particular position withrelation to the prevailing wind.

On the other hand, the dilution of the humid gas by means of outside airis not vital to the process and may be omitted.

In performing the process of this invention, the green hops are firstloaded upon the reticulated floor. This may be in conformity withpresent practice with the exception that the load may be much deeper,due to the increased eificiency of the process. This, of courseyprovidesa larger output from a given floor. The hops will be arranged asuniformly as possible with regard to density and to depth of the bed,which may generally be in the neighborhood of 45 inches.

Drying is accomplished by blowing mixed air and products of combustionof the fuel through the bed of hops from beneath under the carefullycontrolled conditions which will be described hereinafter. Importantamong these conditions are the velocity of gas flow, the moisturecontent, and the temperature of the gas.

With regard to velocity, I prefer to pass the drying gas through thehops at a velocity of between 25 and 70 feet per minute, since I havefound that velocities within this range secure a substantial benefit inavoidance of crushing of the hops in the lower portions of the bed,which is accomplished by the lifting of the hops in the upper portions.With respect to this action, the upper limit of the velocity is that atwhich the -the upper portion of the bed will still be able,

due to its low relative humidity, to abstract water from the hops in theupper layers. It will be apparent that the slower the air travel, themore likely it is to be saturated before it reaches the upper layers, inwhich event the upper layers will not be properly dried but might evenhave water deposited upon them.

With regard to temperature, the temperature may not be above about 145F., otherwise the hops will be charred or drying may be too rapid. Iprefer that the air be at a temperature between and F.

Obviously, the drier the air, the more effectively it will dry the firsthops with which it comes in contact; however, if the drying gas be toodry, I have found that it is not possible to dry a substantial bed witha satisfactory degree of uniformity; therefore, I prefer that the airused have a relative humidity of between about 10% and about 17%.

'With the above conditions all met, I am able to dry a bed 45 inchesthick, and even thicker, in 15 hours, turning being unnecessary anduniformity of the drying being such that the greatest difierencesbetween samples are in the neighborhood of from 3-8%. with presentprocesses, a difierence of 20% is common.

A surprising thing about my process is the suitability of the mixture ofcombustion gases and air for drying hops, which are notoriouslysensitive and delicate. Those skilled in this art have been verydifficult to convince that hops may be satisfactorily dried with such amixture. However, a considerable amount of experience has proved thatpremium hops may be prepared by the use of my apparatus and theperformance of the process.

Sometimes herein I have referred to the drying gases broadly as air. Itis to be understood that the combustion products of hydrocarbon fuelsare included. Such fuels as coal, natural or producer gas, oil,petroleum derived bottled gases, and gasoline are to be used.

The disclosure contained in my application, Serial No. 8,757 filedFebruary 16, 1948, is incorporated herein by reference.

Iclaim:

1. A process for drying hops comprising disposing a quantity of greenhops in a substantially horizontal bed, burning a hydrocarbon fuel withair to provide a hot gas stream mixing the hot gas stream with a streamof atmospheric air to provide an inert gas stream having a relativehumidity of between 10% and 17% and a temperature between about 125 F.and 140 F., and blowing said inert gas stream upwardly through the greenhop bed at a velocity relative to the bed of between about 25 and 70feet per minute until the moisture content of the hops is less thanabout 10% by weight, the depth of the bed and the gas velocity eachbeing such that (1) the inert gas is in contact with the hops in the bedfor from about 3 to about 7 seconds, and (2) there is secured a partialand substantial lifting of the weight of the bed of hops.

2. A process for drying hops comprising disposing a quantity of greenhops in a substantially horizontal bed, burning a hydrocarbon fuel withair to provide a hot gas stream mixing the hot gas stream with a streamof atmospheric air to provide an inert gas stream having a relativehumidity of about 14% and a temperature of about 135 F., and blowingsaid inert gas stream upwardly through the green hop bed at a velocityrelative to the bed of about 40 feet per minute until the moisturecontent of the hops is less than about by weight, the depth of the bedand the gas velocity each being such that (1) the inert gas is incontact with the hops in the bed for about 5 seconds, and (2) there issecured a partial and substantial lifting of the weight of the bed ofhops.

3. A process for drying hops comprisingdisposing a quantity of greenhops in a substantially horizontal bed about 45 inches deep, burning ahydrocarbon fuel with air to provide a hot.,gas stream mixing the hotgas stream with a stream of atmospheric air to provide an inert gasstream having a relative humidity of about 14% and a temperature ofabout 135 F., and blowing said inert gas stream upwardly through thegreen hop bed at a velocity relative to the bed of about 40 feet perminute and in contact with the hops in the bed for about 5 seconds untilthe moisture content of the hops is less than about 10% by weight, thedepth of the bed-and the gas velocity being such that there is secured apartial and substantial lifting of the weight of the bed of hops. 4

4. A process for drying hops comprising disposing a quantity of greenhops in a substantially horizontal bed, and blowing an inert gasupwardly through the green hop bed at a velocity relative to the bed ofbetween about 25 and '10 feet per minute, until the moisture content ofthe hops is less than about 10% by weight, the depth of the bed and thegas velocity each being such that (1) the inert gas is in contact withthe hops in the bed for from about 3 to about 7 seconds and (2) there issecured a partial and substantial lifting of the weight of the bed ofhops, the air initially having arelative humidity of between 10% and 17%and a temperature between about 125 F, and 140 F.

5. A process for drying hops comprising disposing a quantity of greenhops in a substantially horizontal bed, and blowing an inert gasupwardly through the green hop bed at a velocity relative to the-bed ofabout 40 feet per minute until the moisture content of the hops is lessthan about 10% by weight, the depth of the bed and the gas velocity eachbeing such that (1) the inert gas is in contact with the hops in the bedfor about 5 seconds and (2) there is secured a partial and substantiallifting of the weight of the bed of hops, the air initially having arelative humidity of about 14% and a temperature of about 135 F. i

6. A process for drying hops comprising disposing a quantity of greenhops in a, substantially horizontal bed about inches deep, and blowingan inert gas upwardly through the green hop bed at a velocity relativeto the bed of about 40 feet per minute and in contact with the hops inthe bed for about 5 seconds, until the moisture content of the hops isless than about 10% by weight, the air initially having a relativehumidity of about 14% and a temperature of about F., and the depth ofthe bed and the gas velocity being such that there is secured a partialand Zubstantial lifting of the. weight of the bed of ops.

VERIJN A. BLOXHAM.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 37,403 Marsh Jan. 13, 1863198,875 Edgerton Jan. 1, 1878 655,330 Dowdeli Aug. 7, 1900 1,224,560Needham et a1. May 1, 1917 1,226,052 Benjamin May 15, 191'! 1,713,619Owen May 21, 1929 2,231,445 Grapp Feb. 11, 1941 2,422,987 Roberts June24, 1947 OTHER REFERENCES Fan Engineering published by Buffalo ForgeC0,, Copyright 1925, pages 219-22.

